Exhaust component having multiple-plated outer shell

ABSTRACT

A housing for an exhaust component having a longitudinal axis, an outer shell, an inner shell positioned within the outer shell, an expanding joint for permitting relative longitudinal movement of the inner and outer shells in response to temperature differences between the inner and outer shells, and an expanding joint for permitting relative circumferential movement of the inner and outer shells in response to temperature differences between the inner and outer shells.

This application claims the benefit of Provisional Application No.60/091,932, filed Jul. 7, 1998.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to mufflers, and particularly to mufflershaving multiple-plated outer shells. More particularly, the presentinvention relates to multiple-plated outer shells having thermalexpansion portions that permit the multiple plates of the outer shell tomove relative to each other.

The flow of exhaust gas through a muffler having a multiple-plated outershell causes the outer shell to heat up due to the high temperature ofthe exhaust gas. Multiple-plated outer shells include an inner platethat is in direct contact with the hot exhaust gas and an outer platethat is insulated from the exhaust gas by the inner plate. Thisarrangement of the inner and outer plates causes the inner plate to heatup faster than the outer plate. As a result, the inner plate expandsrelative to the outer plate. In addition, this arrangement causes theouter plate to cool down faster than the inner plate which results inthe outer plate contracting relative to the inner plate. The relativeexpansion and contraction of the inner and outer plates causescompressive and tensile forces in the inner and outer plates. Thesecompressive and tensile forces are repeated every time the inner plateexpands relative to the outer plate. The compressive forces in the innerplate may cause buckling of the inner plate.

An exhaust component is provided having first and second end caps, aninner shell coupled to the first and second end caps, and an outer shellcoupled to the first and second end caps. A channel is defined betweenthe inner shell and one of the first and second end caps. A portion ofthe outer shell is positioned in the channel to move longitudinallythrough the channel relative to the inner shell. The outer shellincludes a notch member that is spaced apart from the inner shell. Thenotch member configured to change shape to permit the outer shell tomove circumferentially relative to the inner shell.

Additional objects, features, and advantages of the invention willbecome apparent to those skilled in the art upon consideration of thefollowing detailed description of the preferred embodiments exemplifyingthe best mode of carrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the following figures inwhich:

FIG. 1 is a perspective view of a muffler including a multiple-platedouter shell having an inner plate and an outer plate, a left end capbeing coupled to a left side of the outer shell, a right end cap beingcoupled to a right side of the outer shell, an inlet tube being coupledto the left end cap, and an outlet tube being coupled to the right endcap;

FIG. 2 is a side elevation view of the muffler of FIG. 1;

FIG. 3 is a sectional view taken along line 3—3 of FIG. 2 showing theinner and outer plates of the outer shell being lockseamed togetheralong a top side of the outer shell and the outer plate being formed toinclude a notch member that extends along a bottom side of the outershell and defines a longitudinally extending circumferential expansionportion, the notch member defining a gap between the inner and outerplates to allow the inner plate to expand or contract circumferentiallyoutwardly or inwardly relative to the outer plate.

FIGS. 4-7 are sectional views taken along line 4—4 of FIG. 2 showing howthe notch member defining the circumferential expansion portion adjuststo compensate for the expansion of the inner plate circumferentiallyoutwardly relative to the outer plate as the inner plate heats uprelative to the outer plate under various conditions;

FIG. 4 is an enlarged sectional view of the circumferential expansionportion shown in FIG. 3 taken along line 4—4 of FIG. 2 showing the innerand outer plates at approximately the same temperature so that the innerplate is in an unexpanded state relative to the outer plate and thecircumferential expansion portion is in an ambient condition with thegap between the inner and outer plates being at a maximum distance;

FIG. 5 shows the circumferential expansion portion of FIG. 4 with amoderate amount of heat being applied to the inner plate so that theinner plate is in a slightly expanded state relative to the outer plate,the notch member is slightly flattened relative to the inner plate toaccommodate the outwardly expanding inner plate, and the gap between theinner and outer plates being slightly smaller than in FIG. 4;

FIG. 6 shows the circumferential expansion portion of FIG. 5 with anintense amount of heat being applied to the inner plate so that theinner plate is in a significantly expanded state relative to the outerplate, the notch member is significantly flattened relative to the innerplate, and the gap between the inner and outer plates being slightlysmaller than in FIG. 5;

FIG. 7 shows the circumferential expansion portion of FIG. 6 withintense heat being applied to the inner plate and cold drops of waterhitting the outer plate so that the inner plate is in a maximallyexpanded state relative to the outer plate, the notch member beingmaximally flattened relative to the inner plate, and the gap between theinner and outer plates being at a minimum;

FIGS. 8-11 and 12-15 are sectional views taken along lines 8—8 and12—12, respectively, of FIG. 1 showing a different portion of thecircumferential expansion portion and a first circumferentiallyextending longitudinal expansion portion adjusting to compensate forrelative expansion and contraction of the inner and outer plates;

FIG. 8 is a sectional view taken along line 8—8 of FIG. 1 showing theleftmost portion of the longitudinally extending circumferentialexpansion portion and the bottom-most portion of the firstcircumferentially extending longitudinal expansion portion, the firstlongitudinal expansion portion being defined as the portion of themuffler where the left end cap is lockseamed with the left side of theouter shell to define a circumferentially extending channel between theinner plate and left end cap for receiving the outer plate, the firstlongitudinal expansion portion and the circumferential expansion portionboth being in an ambient condition with the inner plate, left end cap,and outer plate being at approximately the same temperature so that theinner plate and left end cap are in an unexpanded state relative to theouter plate, the gap of the circumferential expansion portion being at amaximum, and the outer plate extending a maximum distance into thechannel defined between the inner plate and end cap;

FIG. 9 is a sectional view similar to FIG. 8 showing a moderate amountof heat being applied to the inner plate and left end cap so that theinner plate and left end cap are in a slightly expanded state relativeto the outer plate and, to accommodate the slightly outwardly expandinginner plate and left end cap, the circumferential expansion portionbeing slightly flattened relative to the inner plate and the outer platebeing slid slightly longitudinally inwardly within the channel away fromthe left end cap;

FIG. 10 is a sectional view similar to FIG. 9 showing an intense amountof heat being applied to the inner plate and left end cap so that theinner plate and left end cap are in a significantly expanded staterelative to the outer plate and, to accommodate the significantlyoutwardly expanding inner plate and left end cap, the circumferentialexpansion portion being significantly flattened relative to the innerplate and the outer plate being slid significantly longitudinallyinwardly within the channel away from the left end cap;

FIG. 11 is a sectional view similar to FIG. 10 showing an intense amountof heat being applied to the inner plate and left end cap and cold dropsof water hitting the outer plate so that the inner plate and left endcap are in a maximally expanded state relative to the outer plate and,to accommodate the maximally outwardly expanding inner plate and leftend cap, the circumferential expansion portion being 15 maximallyflattened relative to the inner plate and the outer plate being slidmaximally longitudinally inwardly within the channel away from the leftend cap;

FIG. 12 is a sectional view taken along line 12—12 of FIG. 1 showinganother portion of the first longitudinal expansion portion, the innerplate, left end cap, and outer plate being at approximately the sametemperature so that the inner plate and left end cap are in anunexpanded state relative to the outer plate, and the first longitudinalexpansion portion being in an ambient condition with the outer plateextending the maximum distance into the channel;

FIG. 13 is a sectional view similar to FIG. 12 showing a moderate amountof heat being applied to the inner plate and left end cap so that theinner plate and left end cap are in a slightly expanded state relativeto the outer plate and the outer plate being slid slightlylongitudinally inwardly within the channel away from the left end cap;

FIG. 14 is a sectional view similar to FIG. 12 showing an intense amountof heat being applied to the inner plate and left end cap so that theinner plate and left end cap are in a significantly expanded staterelative to the outer plate and the outer plate being slid significantlylongitudinally inwardly within the channel away from the left end cap;

FIG. 15 is a sectional view similar to FIG. 12 showing an intense amountof heat being applied to the inner plate and left end cap and cold dropsof water hitting the outer plate so that the inner plate and left endcap are in a maximally expanded state relative to the outer plate andthe outer plate being slid maximally longitudinally inwardly within thechannel away from the left end cap;

FIGS. 16-19 and 20-23 are sectional views taken along lines 16—16 and20—20, respectively, of FIG. 1 showing a second circumferentiallyextending longitudinal expansion portion under the same conditions shownin FIGS. 8-15 for the first circumferentially extending longitudinalexpansion portion;

FIG. 16 is a sectional view taken along line 16—16 of FIG. 1 showing theright-most portion of the longitudinally extending circumferentialexpansion portion and the bottom-most portion of the secondcircumferentially extending longitudinal expansion portion, the secondlongitudinal expansion portion being defined as the portion of themuffler where the right end cap is lockseamed with the right side of theouter shell to define a circumferentially extending channel between theinner plate and right end cap for receiving the outer plate, the secondlongitudinal expansion portion and the circumferential expansion portionboth being in an ambient condition with the inner plate, right end cap,and outer plate being at approximately the same temperature so that theinner plate and right end cap are in an unexpanded state relative to theouter plate, the gap of the circumferential expansion portion being at amaximum, and the outer plate extending a maximum distance into thechannel;

FIG. 17 is a sectional view similar to FIG. 16 showing a moderate amountof heat being applied to the inner plate and right end cap so that theinner plate and right end cap are in a slightly expanded state relativeto the outer plate and, to accommodate the slightly outwardly expandinginner plate and right end cap, the circumferential expansion portionbeing slightly flattened relative to the inner plate and the outer platebeing slid slightly longitudinally inwardly within the channel away fromthe right end cap;

FIG. 18 is a sectional view similar to FIG. 17 showing an intense amountof heat being applied to the inner plate and right end cap so that theinner plate and right end cap are in a significantly expanded staterelative to the outer plate and, to accommodate the significantlyoutwardly expanding inner plate and right end cap, the circumferentialexpansion portion being significantly flattened relative to the innerplate and the outer plate being slid significantly longitudinallyinwardly within the channel away from the right end cap;

FIG. 19 is a sectional view similar to FIG. 18 showing an intense amountof heat being applied to the inner plate and right end cap and colddrops of water hitting the outer plate so that the inner plate and rightend cap are in a maximally expanded state relative to the outer plateand, to accommodate the maximally outwardly expanding inner plate andright end cap, the circumferential expansion portion being maximallyflattened relative to the inner plate and the outer plate being slidmaximally longitudinally inwardly within the channel away from the rightend cap;

FIG. 20 is a sectional view taken along line 20—20 of FIG. 1 showinganother portion of the second longitudinal expansion portion, the innerplate, right end cap, and outer plate being at approximately the sametemperature so that the inner plate and right end cap are in anunexpanded state relative to the outer plate, and the secondlongitudinal expansion portion being in an ambient condition with theouter plate extending the maximum distance into the channel;

FIG. 21 is a sectional view similar to FIG. 20 showing a moderate amountof heat being applied to the inner plate and right end cap so that theinner plate and right end cap are in a slightly expanded state relativeto the outer plate and the outer plate being slid slightlylongitudinally inwardly within the channel away from the right end cap;

FIG. 22 is a sectional view similar to FIG. 20 showing an intense amountof heat being applied to the inner plate and right end cap so that theinner plate and right end cap are in a significantly expanded staterelative to the outer plate and the outer plate being slid significantlylongitudinally inwardly within the channel away from the right end cap;

FIG. 23 is a sectional view similar to FIG. 20 showing an intense amountof heat being applied to the inner plate and right end cap and colddrops of water hitting the outer plate so that the inner plate and rightend cap are in a maximally expanded state relative to the outer plateand the outer plate being slid maximally longitudinally inwardly withinthe channel away from the right end cap; and

FIG. 24 is a block diagram of an exhaust component in accordance withthe present invention, the exhaust component including an inner plate,an outer plate, a longitudinal expansion portion, and a circumferentialexpansion portion.

DETAILED DESCRIPTION OF THE DRAWINGS

A muffler 10 is shown in FIGS. 1-3. Muffler 10 preferably includes aleft end cap 18, a right end cap 20, a plurality of exhaust tubes 22,24, 26, an oval-shaped baffle plate 28 (shown in FIG. 3), and amultiple-plated outer case 16 having an inner shell or plate 30 and anouter shell or plate 32. Muffler 10 also includes a longitudinallyextending circumferential expansion portion 12 and two circumferentiallyextending longitudinal expansion portions 14, 15 that permit inner andouter plates 30, 32 of outer case 16 to move relative to each other.“Longitudinally” is defined herein as lengthwise between left and rightsides 34, 36 of muffler 10 along or parallel to a longitudinal axis 58that runs through a center 59 of muffler 10 in an outward direction 61or an inward direction 62, as shown in FIG. 2. “Circumferentially” isdefined herein as perpendicular to longitudinal axis 58 in an outwarddirection 56 or an inward direction 57 as shown in FIGS. 2 and 3.

The left and right end caps 18, 20 and outer case 16 comprise a mufflerhousing. Left end cap 18 is lockseamed to left side 34 of outer case 16,as shown in FIG. 1, and has an inner surface 88 and an outer surface 90,as shown in FIGS. 1 and 8-15. Inner surface 88 of left end cap 18 facestoward right end cap 20, and outer surface 90 of left end cap 18 facesaway from right end cap 20. Left end cap 18 also includes a flat capportion 86 and a folded lockseam portion 87 surrounding cap portion 86.Cap portion 86 simply closes off the left side 34 of outer case 16 asshown in FIG. 1. Lockseam portion 87 includes a lockseam joint (or bend)89 between the left end cap 18 and the inner plate 30 so that a channel84 is defined within the lockseam portion 87 for receiving the outerplate 32 as shown in FIGS. 8-15.

Right end cap 20 is similar to left end cap 18 and is lockseamed to aright side 36 of outer case 16 in a similar manner as left end cap 18 islockseamed to outer case 16. Right end cap 20, as shown in FIGS. 16-23,has an inner surface 96 and an outer surface 98. Inner surface 96 facestowards left end cap 18 and outer surface 98 faces away from left endcap 18. Right end cap 20 also includes a flat cap portion 94 and afolded lockseam portion 95 surrounding cap portion 94. Lockseam portion95 includes a lockseam joint (or bend) 97 between the right end cap 20and the inner plate 30 so that a channel 85 is defined within thelockseam portion 95 for receiving the outer plate 32 as shown in FIGS.8-15.

Inlet tube 22, interior tube 24, and outlet tube 26, shown in FIGS. 1and 3, permit exhaust fumes or gas to pass through muffler 10. As shownin FIG. 1, inlet tube 22 extends through; a hole or aperture 91 formedin cap portion 86 of left end cap 18 to allow exhaust fumes (not shown)to enter muffler 10. Within muffler 10, as shown in FIG. 3, exhaustfumes pass from inlet tube 22 to outlet tube 26 via interior tube 24.Interior tube 24 extends through the center 59 of outer case 16 andsimply transfers exhaust fumes from inlet tube 22 to outlet tube 26.Outlet tube 26 extends through a hole (not shown) formed in right endcap 20, as shown in FIG. 1, to allow the exhaust fumes to exit muffler10.

Baffle plate 28, shown in FIG. 3, is a flat, oval-shaped piece ofmaterial that is coupled to inner plate 30. Baffle plate 28 ispositioned to lie approximately half way between the left and right endcaps 18, 20 within multiple-plated outer case 16. Baffle plate 28 helpssupport exhaust tubes 22, 24, 26 in the proper position relative toouter case 16. In alternative embodiments, any number or types of tubes,baffles, stamp-formed plates, or other exhaust-gas-directing mechanismsmay be used with the present invention.

Multiple-plated outer case 16 of muffler 10 includes an inner plate 30and an outer plate 32 and has a left side 34, a right side 36, a topside 38, a bottom side 40, a front side 46, and a back side 48, as shownin FIG. 1. Inner plate 30 is positioned to lie inside and adjacent toouter plate 32, as shown in FIGS. 1 and 3. As shown in FIG. 3, inner andouter plates 30, 32 of multiple-plated outer case 16 extendcircumferentially around oval-shaped baffle plate 28 and are lockseamedtogether along top side 38 of multiple-plated outer case 16.

Inner and outer plates 30, 32 each have an inner surface 42, 52 and anouter surface 44, 54, respectively, as shown in FIG. 3. Inner surface 42of inner plate 30 abuts a perimeter surface 60 of oval-shaped baffleplate 28 and inner surface 52 of outer plate 32 abuts outer surface 44of inner plate 30 so that outer plate 32 is in a close-fittingconnection with inner plate 30. The close-fitting connection betweenouter plate 32 and inner plate 30, however, does allow for air (notshown) to thermally insulate inner plate 30 from outer plate 32 toprovide resistance to thermal conductivity, as described below. Thus,inner plate 30, outer plate 32, and baffle plate 28 substantially abutone another so that outer case 16 is substantially oval-shaped as shownin FIG. 3. Inner plate 30, outer plate 32, and baffle plate 28 may bemade out of the same material (e.g., 409 stainless steel) or differenttypes of material.

As shown in FIGS. 1-3, outer plate 32 is formed to include a notchmember 64 that extends along bottom side 40 of outer case 16. Notchmember 64 defines circumferential expansion portion 12 that allows outerplate 32 to flex circumferentially outwardly relative to inner plate 30in direction 56 or inwardly relative to inner plate 30 in direction 57(shown in FIG. 3) to accommodate any thermal expansion or contractionthat occurs due to temperature differences between inner plate 30 andouter plate 32. As shown best in FIGS. 1 and 3, notch member 64 includesa front wall 66, a back wall 67, a bottom wall 68, a left wall 69, and aright wall 70. As shown in FIGS. 3-7, front and back walls 66, 67 haveapproximately the same dimensions and are configured to projectoutwardly away from inner plate 30 so that bottom wall 68 is spacedapart from of inner plate 30.

A plurality of joints 72, 73, 74, 75 interconnects walls 66, 67, 68 ofnotch member 64 as shown in FIG. 4. Outwardly projecting front and backwalls 66, 67 originate at first and second joints 72, 73 respectively,and terminate at third and fourth joints 74, 75, respectively. Front andback walls 66, 67 project slightly towards one another so that first andsecond joints 72, 73 are spaced farther apart from one another than arethird and fourth joints 74, 75. Bottom wall 68 extends between left andright side walls 66, 67 at third and fourth joints 74, 75, respectively,and is substantially parallel to inner plate 30. A gap 76 having a depth78 is formed between inner plate 30 and bottom wall 68 of outer plate 32as a result of notch member 64 being formed in outer plate 32. Thus,circumferential expansion portion 12 is defined by notch member 64interacting with inner plate 30 to form a trapezoid-shaped gap 76extending longitudinally parallel to longitudinal axis 58 between leftand right end caps 18, 20 as shown in FIGS. 1 and 4.

Outer plate 32 further includes first and second channel-engagingportions 80, 82 which are coupled to inner plate 30 and end caps 18, 20,as shown in

FIGS. 8-23. As shown in FIGS. 8-23, the inner plate 30 and outer plate32 are substantially sealed from moisture and contaminants. The leftwall 69 and right wall 70 of notch member 64 shown in FIG. 1,interconnect the front, back, and bottom walls 66, 67, 68 of notchmember 64 to first and second channel-engaging portions 80, 82. As shownin FIGS. 8-11, left wall 69 extends from a fifth joint 81 at bottom wall68 to a sixth joint 83 at first channel-engaging portion 80. Firstchannel-engaging portion 80 abuts inner plate 30 and left end cap 18, asshown in FIGS. 8-15. The operation of first channel-engaging portion 80will be described in more detail below. As shown in FIGS. 16-19, theright wall 70 of notch member 64 extends from a seventh joint 77 atbottom wall 68 to an eighth joint 79 at second channel-engaging portion82 of outer plate 32. Similar to first channel-engaging portion 80,second channel-engaging portion 82 abuts inner plate 30 and right endcap 20.

Circumferential expansion portion 12 allows inner plate 30 and outerplate 32 to move relative to one another in response to thermalexpansion or contraction. As shown in FIGS. 4-11 and 16-19,circumferential expansion portion 12 moves from a steady-state condition(FIGS. 4, 8, 16) when inner and outer plates 30, 32 are at ambienttemperature towards a maximum-adjusting condition (FIGS. 7, 11, 19) wheninner plate 30 is hotter than outer plate 32. As can be seen from FIGS.4-11 and 16-19, circumferential expansion portion 12 acts as a spring tocompensate for circumferential thermal expansion or contraction of innerplate 30 relative to outer plate 32. The transitions of circumferentialexpansion portion 12 are described below as they would occur undernormal operating conditions. The examples used below are onlyrepresentative of the conditions that may cause thermal expansion orcontraction and do not limit the scope of the invention.

In operation, circumferential expansion portion 12 allows outer plate 32to flex circumferentially outwardly in direction 56 when inner plate 30heats up faster than outer plate 32 or when outer plate 32 cools downmore quickly than inner plate 30. For example, when inner plate 30 heatsup faster than outer plate 32, inner plate 30 expands outwardly relativeto outer plate 32 in direction 56 and circumferential expansion portion12 accommodates this expansion of inner plate 30 relative to outer plate32 by allowing outer plate 32 to flex circumferentially outwardly indirection 56. Similarly, when outer plate 32 cools down more quicklythan inner plate 30, outer plate 32 contracts relative to inner plate 30in direction 57 and circumferential expansion portion 12 accommodatesthis contraction of outer plate 32 relative to inner plate 30 byallowing outer plate 32 to flex circumferentially outwardly in direction56. An example will now be used to illustrate this relative expansionand contraction of inner and outer plates 30, 32.

Before an engine that is coupled to muffler 10 is started, inner andouter plates 30, 32 of muffler 10 are at the ambient temperature.Because inner and outer plates 30, 32 are at the same temperature, innerplate 30 is not expanding or contracting relative to outer plate 32 andouter plate 32 is not expanding or contracting relative to inner plate30. Therefore, inner plate 30 is not pushing outwardly on outer plate 32due to thermal expansion and outer plate 32 is not pushing inwardly oninner plate 30 due to thermal contraction. In this condition, shown inFIGS. 3 and 4, side walls 66, 67 of circumferential expansion portion 12extend away from inner plate 30 so that third and fourth joints 74, 75are just slightly closer to one another than are first and second joints72, 73. Thus, when circumferential expansion portion 12 is in asteady-state condition, gap 76 has relatively large depth 78, and notchmember 64 is trapezoid-shaped.

When the engine is initially started and heated exhaust fumes begin toflow through muffler 10, a moderate amount of heat 210 is applied toinner plate 30, as shown in FIG. 5. Because the heated exhaust fumes arein direct contact with inner plate 30 and because inner plate 30 isinsulated from outer plate 32 by air (not shown), inner plate 16 heatsup faster than outer plate 18. Thus, when the engine is initiallystarted, inner plate 30 is at a slightly higher temperature than outerplate 32 and inner plate 30 expands outwardly relative to outer plate 32in direction 56 (because inner and outer plates 30, 32 are preferablymade from the same material). This causes inner plate 30 to pushcircumferentially outwardly relative to outer plate 32 in direction 56against outer plate 32.

Circumferential expansion portion 12 accommodates this circumferentialthermal expansion of inner plate 30 by allowing outer plate 32 to flexcircumferentially outwardly in direction 56 in response to inner plate30 pushing outwardly in direction 56 on outer plate 32. As inner plate30 initially begins to push outwardly on outer plate 32, circumferentialexpansion portion 12 begins to flatten relative to inner plate 30 andcircumferential expansion portion 12 assumes an initial-warm-upcondition which is shown in FIG. 5. As shown in FIG. 5, circumferentialexpansion portion 12 begins to flatten relative to inner plate 30because first and second joints 72, 73 move away from one another andside walls 66, 67 become flatter relative to inner plate 30 as innerplate 30 pushes against outer plate 32 in direction 56. This causesbottom wall 68 to move slightly closer to inner plate 30 which resultsin the depth 78 of gap 76 decreasing. Because inner plate 30 is pushingoutwardly on outer plate 32 due to thermal expansion, side walls 66, 67of expansion portion 12 are pushed apart and become flatter relative toinner plate 30 so that bottom wall 68 is pulled closer to inner plate30. This allows outer plate 32 to act as a spring to compensate for thethermal expansion.

As the engine continues to warm up, an intense amount of heat 212 isapplied to inner plate 30, as shown in FIG. 6, and circumferentialexpansion portion 12 continues to flatten until it reaches amaximum-warm-up condition which is shown in FIG. 6. As circumferentialexpansion portion 12 transitions from the position shown in FIG. 5 tothe position shown in FIG. 6, inner plate 30 continues to expandoutwardly relative to outer plate 32 because the temperature differencebetween inner plate 30 and outer plate 32 continues to increase. Innerand outer plates 30, 32 are both expanding outwardly because both areincreasing in temperature, however, inner plate 30 is expanding at afaster rate than outer plate 32 and therefore inner plate 30 isexpanding outwardly relative to outer plate 32. Thus, because innerplate 30 is expanding outwardly relative to outer plate 32 as the engineinitially warms up, circumferential expansion portion 12 continues tomove closer to the maximum-warm-up condition of FIG. 6.

When circumferential expansion portion 12 reaches the maximum-warm-upcondition (shown in FIG. 6), inner plate 3 0 is increasing intemperature at the same rate as outer plate 32. At this point, innerplate 30, although still getting hotter, is beginning to slow down intemperature rate increase. In other words, inner plate 30 and outerplate 32 are still expanding outwardly, but both are expanding outwardlyat the same rate. Therefore, at this point, as shown in FIG. 6,circumferential expansion portion 12 is at a maximum-warm-up conditionwhere the temperature difference between inner plate 30 and outer plate32 is at a maximum for the warm-up process.

From this point, under normal operating conditions (i.e., where theengine and muffler 10 are warmed up in a controlled environment and coldwater is not splashed on outer plate 32), outer plate 32 begins toincrease in temperature at a faster rate than inner plate 30 because theexhaust fumes have warmed inner plate 30 up to (or close to) thetemperature of the exhaust fumes. The rate at which inner plate 30 isincreasing in temperature begins to slow down, while the rate at whichouter plate 32 is increasing in temperature continues to increase. Inaddition, the rate of temperature increase of the inner plate 30 beginsto decrease relative to the rate of temperature increase of the outerplate 32. As a result, the temperature difference between inner plate 30and outer plate 32 begins to decrease and outer plate 32 begins toexpand outwardly relative to inner plate 30.

This reduction in temperature difference between inner and outer plates30, 32 causes circumferential expansion portion 12 to begin totransition back towards the initial-warm-up condition of FIG. 5.Circumferential expansion portion 12 will continue to transition fromthe maximum-warm-up condition (shown in FIG. 6) towards theinitial-warm-up condition (shown in FIG. 5) as the engine continues towarm up because the outer plate 32 is expanding outwardly relative toinner plate 30 and, as a result, inner plate 30 no longer pushesoutwardly against outer plate 32. However, circumferential expansionportion 12 will not transition all the way back to the steady-statecondition of FIG. 4 even when the engine is completely warmed up becauseinner plate 30 remains at a higher temperature than outer plate 32because of the resistance to thermal conductivity between inner plate 30and outer plate 32. Thus, when the engine is completely warmed up,circumferential expansion portion 12 is at a steady-state warmed-upcondition which can be any position between FIGS. 4 and 6, but mostlikely between FIGS. 5 and 6.

Circumferential expansion portion 12 will remain in this steady-statewarmed-up condition (somewhere between FIGS. 4 and 6) as long as thetemperature difference between inner and outer plates 30, 32 remainsconstant. However, under normal operating conditions, the muffler 10could be splashed by cold water 214 which would hit outer plate 32. Thiswould cause circumferential expansion portion 12 to become even flatteras shown by the maximum-adjusting condition of FIG. 7. When muffler 10is splashed by cold water 214, outer plate 32 is cooled down relative toinner plate 30 and thus outer plate 32 contracts relative to inner plate30 so that outer plate 32 begins pushing inwardly in direction 57against inner plate 30. Circumferential expansion portion 12accommodates this thermal contraction of outer plate 32 relative toinner plate 30 by transitioning from the position shown in FIG. 6towards the position shown in FIG. 7. Specifically, when outer plate 32becomes colder than inner plate 30, outer plate 32 pushes inwardly oninner plate 30 in direction 57 and expansion portion 12 becomes flatterrelative to inner plate 30 to compensate for the thermal contraction ofouter plate 32 relative to inner plate 30. Circumferential expansionportion 12 becomes flatter because first and second joints 72, 73 moveaway from one another, side walls 66, 67 become flatter relative toinner plate 30, bottom wall 68 moves closer to inner plate 30, and thedepth 78 of gap 76 decreases as shown in FIG. 7.

FIGS. 8-11 and 16-19 provide a different sectional view, respectively,of circumferential expansion portion 12 than FIGS. 4-7 which were justdescribed. In addition to showing circumferential expansion portion 12,FIGS. 8-23 also illustrate longitudinal expansion portions 14, 15.

As in circumferential expansion portion 12, longitudinal expansionportions 14, 15 also accommodate relative thermal expansion andcontraction of inner and outer plates 30, 32 of outer case 16. Whilecircumferential expansion portion 12 accommodates circumferentialthermal expansion or contraction in directions 56, 57, as shown in FIG.3, longitudinal expansion portions 14, 15 accommodate longitudinalthermal expansion or contraction in directions 61, 62, as shown in FIG.1.

As shown in FIGS. 8-15, longitudinal expansion portion 14 is the portionof muffler 10 where left end cap 18 is lockseamed with left side 34 ofouter case 16. The lockseam between left end cap 18 and outer case 16extends around the circumference of outer case 16 as shown in FIG. 1.FIGS. 8-11, which are sectional views taken along line 8—8 of FIG. 1,show a portion of longitudinal expansion portion 14 wherecircumferential expansion portion 12 can also be seen. FIGS. 20-23,which are taken along line 20—20 of FIG. 1, show that longitudinalexpansion portion 14 also extends around the entire circumference ofouter case 16, even where circumferential expansion portion 12 is notpresent (i.e., along the front side 46, top side 38, and back side 48).

Left end cap 18 is lockseamed with outer case 16 to define a channel 84within the lockseam between outer surface 44 of inner plate 30 and outersurface 90 of left end cap 18. Channel 84 extends around thecircumference of the left side 34 of outer case 16 and is sized to allowfirst channel-engaging portion 80 of outer plate 32 to be in slidingengagement with inner plate 30 of left end cap 18. Channel 84 onlypermits outer plate 32 to slide longitudinally in directions 61, 62 andis of sufficient length so that outer plate 32 will not slide out ofchannel 84 when thermal expansion or contraction occurs as describedbelow.

The operation of longitudinal expansion portion 14 will now be explainedwith reference to the same operating conditions as were previouslydescribed for circumferential expansion portion 12. As shown in FIGS.8-15, longitudinal expansion portion 14 transitions from a steady-statecondition (shown in FIGS. 8 and 12) towards a maximum-adjustingcondition (shown in FIGS. 11 and 15) to accommodate longitudinal thermalexpansion or contraction of inner plate 30 relative to outer plate 32 indirections 61, 62 (shown in FIG. 1) when the following conditions occur.

Before the engine is started, inner and outer plates 30, 32 are at anambient temperature and longitudinal expansion portion 14 is in asteady-state condition which is shown in FIGS. 8 and 12. In thiscondition, first channel-engaging portion 80 of outer plate 32 extendsalmost entirely into channel 84 a distance 100 so that a major portionof outer surface 54 of first channel-engaging portion 80 engages outersurface 90 of left end cap 18.

When the engine is started and heated exhaust fumes begin to flowthrough muffler 10, longitudinal expansion portion 14 begins totransition from the steady-state condition shown in FIGS. 8 and 12towards an initial-warm-up condition shown in FIGS. 9 and 13. As shownin FIGS. 9 and 13, when the engine is started, a moderate amount of heat210 is applied to inner plate 30 and left end cap 18 which makes innerplate 30 and left end cap 18 just slightly hotter than outer plate 32.This temperature difference causes inner plate 30 and left end cap 18 toexpand longitudinally outwardly relative to outer plate 32 in direction61. As a result, outer plate 32 slides longitudinally inwardly withinchannel 84 away from left end cap 18 in direction 62. Longitudinalexpansion portion 14 accommodates this expansion of inner plate 30 andleft end cap 18 relative to outer plate 32 by allowing inner plate 30and left end cap 18 to move longitudinally outwardly in direction 61away from outer plate 32. Thus, as the engine initially heats up, firstchannel-engaging portion 80 of outer plate 32 slides within channel 84away from left end cap 18 in direction 62 until a smaller portion offirst channel-engaging portion 80 engages outer surface 90 of left endcap 18, as shown in FIGS. 9 and 13. In FIGS. 9 and 13, firstchannel-engaging portion 80 extends into channel 84 a distance 101 whichis smaller than distance 100 in FIGS. 8 and 12.

As the engine continues to warm up, inner plate 30 and left end cap 18continue to increase in temperature more quickly than outer plate 32 andan intense amount of heat 212 is applied to inner plate 30 and left endcap 18, as shown in FIGS. 10 and 14. Thus, inner plate 30 and left endcap 18 continue to expand longitudinally outwardly relative to outerplate 32 in direction 61. Inner and outer plates 30, 32 and left end cap18 are each expanding longitudinally outwardly because each areincreasing in temperature. However, inner plate 30 and left end cap 18are expanding faster than outer plate 32 (because inner plate 30 andleft end cap 18 are in direct contact with the exhaust fumes) andtherefore inner plate 30 and left end cap 18 are expandinglongitudinally outwardly relative to outer plate 32 in direction 61. Asa result, as the engine continues to warm up, channel-engaging portion80 continues to slide out of channel 84 until longitudinal expansionportion 14 reaches a maximum-warm-up condition which is shown in FIGS.10 and 14.

When longitudinal expansion portion 14 reaches the maximum warm-upcondition (FIGS. 10 and 14), inner plate 30; outer plate 32, and leftend cap 18 are all increasing in temperature at the same rate andtherefore expanding at the same rate. At this point, the temperaturedifference between inner plate 30 and outer plate 32 is at a maximum forthe warm-up process. In this condition, shown in FIGS. 10 and 14,channel-engaging portion 80 extends a distance 102 into channel 84which, in the illustrated embodiment, is approximately one-fourth of theway into channel 84.

From this point in the warm-up process, under normal operatingconditions, outer plate 32 begins to increase in temperature at a fasterrate than inner plate 30 and left end cap 18. Inner plate 30, outerplate 32, and left end cap 18 are still each increasing in temperature,but now outer plate 32 begins to increase in temperature at a fasterrate than inner plate 30 and left end cap 18. As a result, outer plate32 starts expanding.outwardly relative to inner plate 32 and left endcap 18 and therefore outer plate 32 begins to slide back into channel 84towards left end cap 18. Thus, longitudinal expansion portion 14 beginsto move back towards the initial-warm-up condition shown in FIGS. 9 and13.

Longitudinal expansion portion 14 continues to transition from themaximum-warm-up condition (FIGS. 10 and 14) towards the initial warm-upcondition (FIGS. 9 and 13) as the engine continues to warm up past themaximum-warm-up condition. However, longitudinal expansion portion 14will not transition all the way back to the steady-state condition(FIGS. 8 and 12) even when the engine is completely warmed up becauseinner plate 30 remains at a higher temperature than outer plate 32 dueto the resistance to thermal conductivity between inner plate 30 andouter plate 32. Thus, when the engine is completely warmed up,longitudinal expansion portion 15 is at a steady-state-warmed-upcondition which can be any position between FIGS. 8, 12 and 10, 14, butmost likely between FIGS. 9, 13 and 10, 14.

Longitudinal expansion portion 14 will remain in thissteady-state-warmed-up condition as long as the temperature differencebetween inner and outer plates 30, 32 remains constant. However, ifmuffler 10 is splashed by a cold puddle causing cold water 214 to hitouter plate 32 when an intense amount of heat 212 is being applied toinner plate 30 and left end cap 18 as shown in FIGS. 11, 15,longitudinal expansion portion 14 begins to transition from thissteady-state-warmed-up condition (between FIGS. 8, 12 and 10, 14)towards the maximum-adjusting condition, (FIGS. 11 and 15). Becauseouter plate 32 is cooled down relative to inner plate 30 when a puddleis hit, outer plate 32 contracts relative to inner plate 30 and, as aresult, first channel-engaging portion 80 begins to slide out of channel84 away from left end cap 18 in direction 62. As a result, longitudinalexpansion portion 14 begins to move towards a maximum-adjustingcondition shown in FIGS. 11 and 15.

Although hitting an extremely cold puddle could cause longitudinalexpansion portion 14 to reach the maximum-adjusting condition of FIGS.11, 15, longitudinal expansion portion 14 could be designed in such away that the maximum adjusting position of FIGS. 11, 15 is neverreached. For example, longitudinal expansion portion 14 could bedesigned to require sub-freezing temperatures so that even under theextreme example just described, the positions of inner and outer plates16, 18 shown in FIGS. 11, 15 would still not be reached. Nevertheless,FIGS. 11, 15 represent a “worst case” condition where there is extremeheating of inner plate 30 and left end cap 18 and extreme cooling ofouter plate 32. This could occur, for example, when muffler 10 hits acold puddle at the exact moment in the warm-up process wherelongitudinal expansion portion 14 is at its maximum-warm-up condition(i.e., FIGS. 10, 14). Thus, from the maximum-warm-up condition of FIGS.10, 14, a cold puddle could cause outer plate 32 to contract relative toinner plate 30 so that the maximum adjusting condition of FIGS. 11, 15is reached (or nearly reached). Therefore, it is not beyond the scope ofthis invention for different events (other than starting a cold engineand/or hitting a puddle) to define the various conditions or states oflongitudinal expansion portion 14 (shown in FIGS. 8-15) so thatlongitudinal expansion portion 14 would be capable of accommodating manycauses of thermal expansion or contraction of inner and outer plates 30,32.

Nevertheless, once outer plate 32 reaches its maximum coldness fromhaving been splashed by a cold puddle after being completely warmed up,outer plate 32 begins to warm back up because of the high temperature ofinner plate 30. Thus, although longitudinal expansion portion 14 may notreach the maximum-adjusting condition shown in FIGS. 11, 15, it doesreach a maximum-puddle-adjusting condition which can be any positionbetween FIGS. 8, 12 and 11, 15. From this maximum-puddle-adjustingcondition, longitudinal expansion portion 14 begins to transition backto the steady-state-warmed-up condition of FIGS. 10, 14. This process issimilar to the process described above when longitudinal expansionportion 14 transitioned from the maximum-warm-up condition of FIGS. 10,14 to the steady-state-warmed-up condition (between FIGS. 8. 12 and 10,14).

Second longitudinal expansion portion 15 is shown in FIGS. 16-23. Secondlongitudinal expansion portion 15 is identical to first longitudinalexpansion portion 14 except that second longitudinal expansion portion15 is the portion of muffler 10 where right end cap 20 is lockseamedwith inner plate 30 of outer case 16. Thus, as shown in FIGS. 16-23,second longitudinal expansion portion 15 includes a lockseam betweenright end cap 20 and right side 36 of outer case 16 defining a channel85 between outer surface 44 of inner plate 30 and outer surface 94 ofright end cap 20 that extends around the circumference of the right side36 of outer case 16. The channel 85 receives second channel-engagingportion 82 of outer plate 32 to allow outer plate 32 to slidelongitudinally relative to inner plate 30 in directions 61, 62 inresponse to thermal heating or cooling. The description of the operationof longitudinal expansion portion 14 with reference to FIGS. 8-15 isidentical to the operation of longitudinal expansion portion 15 shown inFIGS. 16-23, respectively, aside from the difference's just described.

The muffler or exhaust component 10 is shown in block diagram form inFIG. 24. Muffler 10 includes inner plate 30, outer plate 32, acircumferential expansion portion 12, and a longitudinal expansionportion 14. Circumferential expansion portion 12 permits inner and outerplates 30, 32 to move circumferentially relative to one another andlongitudinal expansion portion 14 permits inner and outer plates 30, 32to move longitudinally relative to one another.

Although this invention has been described in detail, variations andmodifications exist within the scope and spirit of the invention asdescribed and as defined in the following claims.

What is claimed is:
 1. An exhaust component having a longitudinal axis,the exhaust component comprising a first end cap, a second end capspaced apart from the first end cap, an inner shell coupled to the firstand second end caps, a channel being defined between the inner shell andone of the first and second end caps, and an outer shell coupled to thefirst and second end caps, a portion of the outer shell being positionedin the channel defined between the inner shell and one of the first andsecond end caps to move longitudinally through the channel relative tothe inner shell, and the outer shell including a notch member that isspaced apart from the inner shell, the notch member being configured tochange shape to permit the outer shell to move circumferentiallyrelative to the inner shell.
 2. The exhaust component of claim 1,wherein the notch member is spaced apart from the inner plate by adistance and the distance between the notch member and inner platechanges as the inner and outer plates move circumferentially relative toeach other.
 3. The exhaust component of claim 1, wherein the notchmember extends longitudinally substantially parallel to the longitudinalaxis of the exhaust component.
 4. The exhaust component of claim 1,wherein the inner shell and outer shell are coupled to substantiallyseal a volume defined between the inner and outer shells.
 5. The exhaustcomponent of claim 1, wherein the outer shell and inner shell arecoupled together in a lockseam.
 6. The exhaust component of claim 1,wherein the inner shell is coupled to the first end cap in a lockseamand to the second end cap in a lockseam.
 7. The exhaust component ofclaim 1, wherein a second channel is defined between the inner shell andthe other of the first and second end caps and the outer shell ispositioned in the second channel to move longitudinally through thesecond channel relative to the inner shell.
 8. An exhaust componenthaving a longitudinal axis, the exhaust component comprising an inletconfigured to receive exhaust gas, an outlet configured to dischargeexhaust gas, a housing, the housing including inner and outer platesthat are movable relative to each other in a longitudinal direction thatis substantially parallel to the longitudinal axis, and an expandingjoint located in one of the inner and outer plates to permit the innerand outer plates to move in a circumferential direction.
 9. The exhaustcomponent of claim 8, wherein the housing further includes first andsecond end caps and the first and second end caps are coupled to theinner and outer plates.
 10. The exhaust component of claim 9, whereinthe first end cap and inner plate define a first channel, the second endcap and inner plate define a second channel, and the outer plate ispositioned to move through the first and second channels as the innerand outer plates move longitudinally relative to each other.
 11. Theexhaust component of claim 9, wherein at least one of the end caps andthe inner plate define a channel and the outer plate is positioned tomove through the channel as the inner and outer plates movelongitudinally relative to each other.
 12. The exhaust component ofclaim 9, wherein at least one of the end caps defines a channel and oneof the inner and outer plates are positioned to move through the channelas the inner and outer plates move longitudinally relative to eachother.
 13. The exhaust component of claim 9, wherein the first andsecond end caps define first and second channels, respectively, and oneof the inner and outer plates are positioned to move through the firstand second channels as the inner and outer plates move longitudinallyrelative to each other.
 14. The exhaust component of claim 9, whereinthe inner plate is coupled to the first end cap in a lockseam and to thesecond end cap in a lockseam.
 15. The exhaust component of claim 8,wherein the expanding joint is placed in the outer plate and includes anotch member that is spaced apart from the inner plate by a distance.16. The exhaust component of claim 15, wherein the distance between thenotch member and inner plate changes as the inner and outer plates moverelative to each other.
 17. The exhaust component of claim 15, whereinthe notch member extends substantially parallel to the longitudinal axisof the exhaust component.
 18. The exhaust component of claim 8, whereinthe inner plate and outer plate are coupled to substantially seal avolume defined between the inner and outer plates.
 19. The exhaustcomponent of claim 8, wherein the outer plate and inner plate arecoupled together in a lockseam.
 20. A housing for an exhaust componenthaving a longitudinal axis, the housing comprising an outer shell, aninner shell positioned within the outer shell, an expanding jointlocated within the outer shell for permitting relative longitudinalmovement of the inner and outer shells in response to temperaturedifferences between the inner and outer shells, and means for permittingrelative circumferential movement of the inner and outer shells inresponse to temperature differences between the inner and outer shells.21. The housing of claim 20, wherein the outer shell and inner shell arecoupled together in a lockseam.
 22. A housing for an exhaust componenthaving a longitudinal axis, the housing comprising an outer shell, aninner shell positioned within the outer shell, and an expanding jointlocated within the outer shell for permitting relative circumferentialmovement of the inner and outer shells in response to temperaturedifferences between the inner and outer shell.